Process of making steel brake drums



July 21,1925. 1,546,656

F. D. HANSEN ET AL I PROCESS OF MAKING STEEL BRAKE DRUMS File Apr l 19243 Sheets-Sheet 1 id AQM'M M 4 July 21, 1925. 1,546,656

F. D. HANSEN ET AL PROCESS OF MAKING STEEL BRAKE DRUMS Filed April 7,1924 3 Shets-Sheet 2 f Law July 21, 1925. 6 1,546,656

- F. D. HANSEN ET AL PROCESS OF MAKING STEEL BRAKE DRUMS File April 19243 Sheets-Sheet 3 Patented July 21 1925.

n. HANSEN AND HERBERT w. TINKER, or MILWAUKEE, wrsoonsnt.

ASSIGNORS TO FEDERAL PRESSED STEEL COMPANY, OF MILWAUKEE, WISCONSIN,

A CORPORATION OF WISCONSIN.

PROCESS OF MAKING STEEIJ BRAKE DRUMS.

Application filed April 7, 1924. 'Seria1 No 704,766.

To all whom it may concern:

Be it known that we, FREDERICK D. HANSEN and HERBERT W. TINKER, bothcitizens of the United States, and residing at Milwaukee, county ofMilwaukee, and State of Wisconsin, have invented certain new and usefulImprovements in the Process of Mak ing Steel Brake Drums, of which thefollowing is a specification.

In the manufacture of brake drums, which are attached to road wheelsandother parts of autom'obiles and the fike, discs are cut or punchedfroma sheet or strip of steel of the required thickness. The discs areplaced in a very powerful compression die, which cups the peripheralportion of each disc over to form the annular flange of the drum withwhich the frictional material of the brake is adapted to contact toeffect the proper braking'action of the vehicle. VVhenthe drums aretaken from the die their webs are bowed slightly outwardly, because inthe pressing ope-ration the bottoms are not pressed flat, althoughthebottom face of the punch may beperfectly flat. We attribute this bowingaction to the fact that the edge of the inner die member engages thefillet or corner radius at the juncture of the webs and their flangesand as this fillet or radius is not sharply defined the bottom face ofthis die member does not.press as firmly against the web as it doesagainst the radius. The bottoms also tend to spring outwardly due tosome resiliency in the steel. The drums are next placed inanother die inwhich the opposed faces of the die members are formed for the purpose ofmaking the web perfectly flat or giving it a slight concavity, that ispressing the web slightly inwardly past the center of the plate in whichthe web would lie were it flat. In many cases, it is necessary tosubject the drums to the action of the second die several times inorderto give them' the proper concavity orflatness,.as the case maybe,within the small'limits required or specified by automobile companies orothers. It is recognized by those skilled in the art, that it isdiflicult, and in many instances nnpossible, to form the brakev drums sothat the brake flanges are concentric, that is circular within therequired limits, and so that the web is symmetrical throughout and freefrom defective or distortive swells or bulges. The

web ofthe drum, when applied, seats firmly against the wheel-hub or sokes of the wheel,

and it is desirable that t is engagement be perfect and that the flangeof the drum be truly concentric so that the flange will be trulv inalignment with the friction shoe or band of the brake in order that themaximum braking effort is accomplished and eq rally distributedthroughout the flange of the brake drum. It frequently happens in themanufacture of brake drums, as formerly practiced, that the flangesof'some drums are so eccentric and the webs have such large bulges orswells causing the eccentricity,

that it is necessary to hammer the bulges with a very heavy hammer, tobring the flanges within the acceptable limits of eccentricity. In someinstances this cannot be done and then the brake drums are scrapped. Webelieve that the difficulty in securing drums which have their flangesconcentric and their webs symmetrical is due to the fact that during thepressing or forming operation of the discs to cup themlto their shapeunequal strains and stresses are set up in the steel and the excessmaterial in the webs. giving the webs their convex or bowed form, exertsa radial force outwardly tending to distort or throw the flange of thedrum out of concentricity. We find that usually these strains aregreatest and cause the maximum distortion in the direction in which thesteel has been rolled, that is in the direction of the grain of thesteel, so that the diameter'of the drum is slightly greater in thisdirection'than it is in the transverse direction, thereby tending togive the flange a slight oval or egg-shape form. The distortiv'e swellsor bulges in the web also seem to be along this greater diameter. Thesubsequent operation giving the webs their proper concavity or flatnessexplained above, in some cases tends to bring the flange towardon'centricity, but this cannot always be accomplished and usually notwithin close limits. The degree of eecentricity depends upon certaincharacteristics of or conditions in the steel, but,-as is well known byexpertswersed in steel making,\though not frilly understood by them,these characteristics or conditions can not be accurately controlled oruniformly regu' lated or obviated. It has, therefore, been necessary inthe past to test or measure the eccentricity of the flange andunevenness of the bearing zone of the web of each and every drum byprecision instruments to determine if they are within the prescribedlimits and then correct, if possible, the defects in these respects ifthe limits are exceeded. The testing and thorough inspection of thedrums, the correcting of defects and scrapping of drums which are badlydefective materially increase the cost of the drums.

The principal object of our invention is to rovide anovel process ofmaking brake drums with substantially truly concentric brake flanges andsubstantially truly sym- -mertical webs and .to this .end we pressridges or ribs, preferably radiating'ones, in thewebs of the drums.

Other advantages of our invention are that the drums are strengthened,and care- .ful tests and inspection are not necessary,

thus reducing the cost of manufacture. Still further advantages of ourinvention will be pointed out hereinafter.

Referring to the drawings, Fig. 1 is a ver tical section through the diemember and punch of a. drum-forming compression die, showing a steeldisc, from which the drum is formed, between the members; Fi' 2illustrates the brake drum after it as been cupped or formed in andremoved from the compression die; Fig. 3 is ayertical section throughthe die member and punch of the die or tool bumping the webs ofthe drumsand forming the ribs therein, the view being taken on the line 33 ofFig. 4; Fig. 4 is a top plan view taken on the line 4-4 of Fig. 3 wlththe brake drum omitted; Fig. 5 is a sectional view taken; through a drumformed by our process, the section being takenv as on the line 5-5 ofFig. 6; Fig. 6 is an inside elevation of a brake drum formed by ourprocess; and Fig. 7 is a view similar to Fig. 6 but shows a modifiedform of brake drum made by our process. I

In practicing our process a steel disc 10 is pressed or formed in asuitable forming compression die, such as is conventionally illustratedin part in Fig. l in which 11 is the die member and 12 is the punch. Thepunch 12 is forced downwardly udder great pressure givin the disc itsbrake-.drum formation, as in icated by dotted lines 10 in this view. 11'indicates the stripper plates for stripping the drums from the punch. InFig. 2 we have shown in sections a brake drum after it has been formedby the forming compression die, but we have somewhat exaggerated theconvexity of the web 13 of the drum in order to illustrate more clearlyits general contour. We next punch the hub opening 6 and the bolt holes7 in the web, such as shown in Figs. 5, 6 and 7. We then place the drumover the member 13 of an-' other die or tool as shown in Fig. 3. In thisfigure we have shown the punch 14 in its lowest position. The die member13 comprises a cylindrical base 13 mounted on any suitable platform 15.Mounted on top of the base 13" is a disc 16 which is fastened to thebase 13 by means of screws 17'projecting through the base 13" andscrewed at their upper ends into the threaded openings in the disc 16. rThe disc 16 is provided with radiating grooves 18 in which are seatedand secured by screws 19 hardened pieces of steel 20 provided withgrooves 21 in their top faces. The upper die member or plunger 14 issecured to a power slide 23 by a screw 24. Secured to the lower face ofthe cylindrical. base 14 of the punch 14 is a disc 25 secured to thebase 14' by screws 26. The lower face of the plate'25 is provided withgrooves 27 in which are seated hardened pieces of steel 28 provided withribs 29 on their bottom faces in alignment with the grooves 21. Themechanism for operating the punch 14 is so designed that the punchimparts a quick and powerful blow to the web of the brake drum and atthe same time the ribs 29 force the metal under them into the grooves21,

thereby forming radiating ribs 30 in the web of the brake drum. It willbe observed that the bottom face of the disc 25 is slightly convex andthe upper faceof the disc 16 is correspondingly concaved in order toimpart a concave contour to the web of the brake drum. It will also beobserved from Fig. 3 that the ribs 29 are of tapering depth, beingdeepest at their inner ends so that the ribs 30 formed in the web of thebrake drum are of tapering depth, being deepest at their in ner ends.

We have shown in Figs. 5, 6 and 7, illustrative forms of drums made bypracticing our process. We preferably form the ribs 30, as shown inthese views, by depressing the metal inwardly, that is on the inside ofthe web so that they do not interfere with or engage the spokes or hubflange of the wheel when the drum is attached to the wheel. It isevident that as the ribs 30 are of tapering depth and are of greatestdepth at their inner ends, the ribs take up the maximum amount of metaladjacent the hub opening and progressively less outwardly. l/Vhile Weprefer that the ribs shall be straight as shown in Figs. 5 and (3, yetthey may be curved, as, for example, illustrated in Fig.7, or they maybe of any other desired and feasibleform or shape, the grooves 21 of thedie and the ribs 29 of the punch being correspondingly formed or shaped.It will be observed that in Fig. 7 the outer circle of bolt holes areradially out of alignment with, that is radially between, the bolt holesof the inner circle, and this is made practical by deflecting the outerportions of the ribs.

We find that in drums made by our improved process, the unequal strainsand stresses, referred to above, are either equally distributed,neutralized ,or eliminated. The ribs take up the surplus or excess metalin the web (which excess gave the web of the drum its initial bowed outcontour or conr existent in the drum before the ribs are formed in itsWeb. This equalization or elimination of the deforming or distorting'strains by the formation of the ribs brings the brake drum flan e to itsproper true concentricity and at t e same time the web is made perfectlysymmetrical throughout. We have found by actual demonstration that it isonly necessary to bump drums by our process once and that the flangesare much more concentric and the webs much more symmetrical thanunribbed drums made from exactly the same sheet or strip of steel. It isnot necessary to test drums made by our process for concentricity orsymmetry or subject them to rigid inspection as the product is uniformand substantially perfect. Thus considerable saving'in the cost ofmanufacture is effected. Furthermore, we have discovered that the ribs,either due to the equal distribution of the strains and stresses or forsome other reason, increase the strength of the flanges so that theymore readily resist distortion or bending, and this is highly importantas they are subjected to considerable force when the braking eflort isapplied to them, and also to rough handling and use in transportationand by workmen in the factories where the drums are assembled on theautomobiles. It will also be obvious that the ribs strengthen the websof the drums radially and axially and that the ribs increase the widthof the bearing surface or edge of the hub opening 6 on the barrel of thewheel hub, as the ends of the ribs form projections 31 as viewed in Fig.5. In securing the brake drum to a wheel, the web of the brake drum isdrawn up tightly against the flange of the hub by means of boltsextending through the openings 7 between the ribs, and as the segmentsbetween the ribs are comparatively narrow adjacent the holes, andseparated by the grooves formed "by the rib the web of the drum is drawnmore easi y and equally against the wheel and the ribs prevent the webfrom springing out past its center plane, (after the fashion of thebottom of a tin dish pan) as is the case in some instances with unribbedbrake drums.

While we have illustrated in the drawings and described in thespecification a preferred form of embodiment of the mechanisms forcarrying out our process, yet it will be understood that the apparatusesare illustrative only as various changes and modifications may madetherein as desired. \Ve also wish it to be understood that while we haveillustrated ,our process as adapted for forming brake drums with concavewebs and radiating ribs pressed inwardl and of tapering formation, itisad-a te in its broader aspect, for the manufac ure of brake drumshaving perfectly'flat webs throughout,

or convex webs,'and that the ribs m extend other than radially or bepressed -outwardly or may be of uniform depth. from one end to theother. 1

\Ve claim: a, 1

1. The process of making steelflhrake drums which consists in pressindiscs to form drums with peripheral bra e'fianges and convex webs andthen bumping the webs and forming ribs in the webs to take up thesurplus metal therein and tend to make the flanges substantially trulyconcentric.

2. The process of making steel brake A ribs of tapering depth in theweb's to take up the surplus metal and tend to make the flangessubstantially truly concentric.

3. The process of making brake drums with substantially truly concentricperipheral flanges and symmetrical webs which consists in imparting asharp blow to the webs and pressing ribs in the webs to eliminate orequalize the distortive strains and stresses.

4. The process of making brake drums with substantially truly concentricflanges and symmetrical webs, which consists in simulta-neousl'imparting a sharp blow to the webs an ressingradiating ribs of taperingdepth m the webs to give the webs the desired concavity or flatness andto eliminate or equalize the distortive strains and stresses.

FREDERICK D.- HANSEN. HERBERT W. -TINKER.

